Organic color pigments provide brilliant, i.e., bright and clean, chroma for yellow, red, orange and green that inorganic color pigments do not provide. In color science, three parameters, brightness (L*), chroma (C*) and hue (H*), are used to represent the qualities of a given color. The C*, which is a measurable parameter, is expressed as the distance of a color in the color space to the central point. The further away a color is from the central point, the larger the C* is and the cleaner or clearer the color is. In a deep base or clear base with little or no inorganic color pigments, organic pigments are the primary choices for achieving bright, clear and highly saturated colors. Blending inorganic white or other color pigments with an organic pigment results in a loss of the brilliant chroma of the organic pigment.
In conventional tint-based paint systems, a single paint product that has been tinted to the desired color is applied to a substrate, e.g., a wall. The paint product having the desired color is obtained by adding from 1 to 15% by volume of color concentrates made with primary color pigments to a tint base. The color concentrates made from organic color pigments typically contain organic color pigment from 1 to 30% by volume. Therefore, a clear base paint with maximum loading of organic pigment load at 15% will contain organic pigment no more than 5% by volume. At these pigment concentrations, however, paint products containing organic yellow, orange, red and green colors lack the opacity necessary to produce the desired color on the substrate and to provide the desired level of hiding of existing substrate colors, markings or patterns. In order to overcome these limitations and to achieve the desired colors and necessary hiding qualities, these paint products are conventionally applied in multiple overlapping coats, for example from at least three to eight or more coats of paint. For example, four to eight coats are required for colors such as yellow, light green, organic red or orange to achieve the desired level of hiding when applied on a white wall containing dark stripes.
Alternate attempts at achieving improved hiding characteristics use a mixture of inorganic pigments and organic pigments in the paint. Although mixtures of organic and inorganic pigment provide the desired color (hue), the brilliant chroma (L* and C*) associated with the organic pigment is decreased. In addition, existing paint systems utilize separate primer coats, e.g., a white primer, to achieve additional hiding of existing substrate colors and pattern, in particular when using the paints that contain poor hiding color pigments. White primer coat paint systems, however, typically require the application of at least one and possibly more primer coats in addition to two or more coats of the tinted paint on top of the white primer to overcome or to hide the white color of the primer coat. In an attempt to improve the hiding capabilities of paint systems that utilize a primer coat in combination with the tinted paint, a small amount of non-white color pigment has been added to the relatively large amount of white pigment in the primer. Although the use of tintable primers results in some improved hiding, the number of coats of the tinted paint that are required to be added over the primer coat is still at least two, and the total number of applied coats is still at least three. Therefore, known methods for utilizing organic pigment colors including yellow, orange and red use (1) three or more tinted coats, or (2) one or multiple coats of white primer or tintable primer in combination with one (if multiple primer coats are used) or multiple coats of tinted top coats. All of these known methods require at least three and possibly more coats to provide a sufficient amount of hiding and to achieve the desired color in the finished painted surface.
Two coat paint systems are found in metal coating or automobile painting applications. Examples of these systems are described in, for example, U.S. Pat. Nos. 5,871,827, 5,025,041 and 5,830,567. These systems, however, utilize a heavily tinted base in combination with a clear top coat that is transparent or substantially transparent. The clear top coat is applied for purposes of protecting the base coat and imparting a glossy finish. In addition, the clear top coat may include additives such as metallic flakes or minute amounts of pigment that are added to provide the desired effects to the basecoat, for example a pearlescent appearance. The additives do not significantly diminish the transparency of the clear coat, and the clear coat does not contribute to the hiding properties of the base coat.
Therefore a paint product or paint system is needed that provides sufficient hiding of a substrate with only two layers or coats.